Windrow harvesting typically involves sweeping nuts, grains or similar small crops into long rows on a field for drying. For example, after nuts are shaken from trees in an orchard, they are typically swept into windrows three to four feet wide. Harvesters then typically condition the windrows by re-sweeping the rows, removing debris such as rocks or branches. Harvesters then typically collect the crops and bring them to a storage.
In some orchards, growers may add yield monitoring devices to their harvesters, tractors, or similar agricultural vehicles for the precision monitoring of agricultural crops. Yield monitoring devices typically measure the total amount of crop harvested in a windrow by measuring several attributes of the crop as it passes through the device. For example, sensors in a grain yield monitor may measure the total grain harvested by measuring the grain mass flow, moisture content, and the speed of the grain as it passes through the elevator and holding tank of a harvester.
Although some yield monitoring devices have been integrated with GPS devices to associate the yields with geographic information, yield monitoring devices generally do not associate yield with a particular plant. As a result, growers have not been able to fully determine how factors such as environment and disease have or will affect the yield of that plant, and on a larger scale, the orchard as a whole.
Further, the sensors typically used in yield monitoring devices are generally expensive and inaccurate. For example, to measure mass flow of grains passing through a harvester, yield monitoring devices typically use impact plates and load cells. Other yield monitoring devices may also use passive sensors to measure and process ambient light reflected from the measured objects. However, passive sensors are not typically accurate for taking spectral measurements in the field. Typically, inexpensive optical sensors, such as LED sensors, have not been used in precision farming applications because of their low resolution.
Accordingly, a need exists for a low-cost, optically-based yield monitoring device that associates yield with a particular plant or region within a grower's holdings. In particular, a need exists for accurately estimating yield measurements, such as volume, and associating such measurements with high-resolution and precise geodetic positional data.